1. Field of the Invention
The present invention relates to input devices, and especially to a touch pad and a method for regulating sensitivity of the touch pad.
2. Description of Related Art
Touch pads are becoming increasingly popular because of their ease of use, versatility, and low price. A touch pad is often incorporated in electronic devices, such as portable computers, and used as a pointing. The touch pad allows a user to make selections and move a cursor by simply touching an input surface of the touch pad with a finger or a stylus. The touch pad is connected to a processor via a communication link. In general, the touch pad recognizes a location of the touch on the input surface and sends a signal to the processor. The processor performs actions to accept the selections or move the cursor based on the signal. They are different types of touch pads, such as capacitive touch pads, resistive touch pads, surface acoustic wave touch pads, infrared touch pads, etc.
However, changes in atmospheric pressure can affect sensitivity of the touch pad, thus reducing a stability of the touch pad. Take the capacitive touch pad for example, the capacitive touch pad comprises of rows of a first set of conductive traces, and of columns of a second set of conductive traces, and a dielectric insulator. The first set of conductive traces and the second set of conductive traces are insulated by the dielectric insulator to form a grid with an array of capacitors. When a point on the touch pad is touched, the capacitance of the capacitors at that point changes. A subsequent circuit then generates a signal according to the change of capacitance, and the signal can be used to identify the point.
As atmospheric pressure changes, the conductivity of the human body changes. As atmospheric pressure reduces, a coupling capacitance between the human body and the touch pad decreases, and the sensitivity of the touch pad decreases. Similarly, as atmospheric pressure increases, the coupling capacitance between the human body and the touch pad increases, therefore the sensitivity of the touch pad increases. Thus, changes in atmospheric pressure may affect the stability of the touch pad.
Therefore, a touch pad and a method for regulating sensitivity of the touch pad are desired.